Bigcreekite

Chemical formula: BaSi₂O₅·₄H₂O

A hydrated barium silicate forming colorless, platy crystals, known exclusively from one locality worldwide.

## Characteristics Bigcreekite is a hydrated barium silicate, forming very small, thin, platy or micaceous crystals. They typically occur as radial aggregates and rosettes reaching up to 1 mm in diameter. It is a colorless to white mineral with a vitreous luster. ## Physical Properties Its Mohs hardness is about 3-4, making it a relatively soft mineral. It has a density of 2.74 g/cm³, is transparent to translucent, and exhibits perfect cleavage in one direction. ## Colors and Varieties This mineral is colorless or white. No color varieties or commercial forms are distinguished. ## History and Name The name Bigcreekite comes from its discovery locality – Big Creek in Fresno County, California, USA. It was described and approved as a new mineral in 1993 by G.L. Hovis, D.R. Speer, B.L. Gors, and P.H. Benoit. ## Uses Due to its extreme rarity and microscopic crystal sizes, bigcreekite has no industrial applications. It is solely an object of scientific and collecting interest.

Properties

Mohs hardness: 3-4
Luster: Vitreous
Streak: White
Density: 2.74
Cleavage: Perfect on {010}, good on {100} and {001}
Transparency: Transparent to Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Bigcreekite can be preliminarily identified by its characteristic micaceous form, formation of small rosettes, and co-occurrence with other rare barium silicates. However, it is such a rare mineral that its identification in the field is practically impossible. Definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other platy minerals, such as muscovite or talc, but differs from them in hardness, density, and, most importantly, its environment of occurrence. Its association with sanbornite and other barium minerals is a key indicator. ## Crystal Forms It forms thin, tabular or platy crystals, which often combine into radial aggregates, rosettes, or lamellar clusters.

Geological environment

## Genesis Bigcreekite is a secondary mineral. It forms as a result of hydrothermal alteration or weathering of sanbornite (BaSi₂O₅) at low temperatures. This process involves the hydration of the primary barium silicate. ## Mineral Associations This mineral occurs in association with sanbornite, quartz, walstromite, celsian, pellyite, taramellite, fresnoite, gillespite, and witherite. ## Localities The only confirmed locality for bigcreekite worldwide is its type locality – Big Creek in Fresno County, California, USA. It was found there in a single glacial erratic of sanbornite-quartz rock, originating from a glacial moraine.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, the value of a specimen is primarily determined by the abundance of its occurrence (quantity and size of rosettes), crystal habit, and the presence of well-defined associated minerals. The most valuable samples are those with distinct, sharp crystals on a contrasting background. ## Popular Localities The only source of specimens is the type locality in California, which makes them extremely difficult to acquire and primarily found in institutional and specialized collections.

Care and storage

## Cleaning Specimens should be cleaned very carefully, preferably with a soft brush dry to remove dust. If liquid is necessary, distilled water is recommended, but prolonged soaking should be avoided. ## What to Avoid Avoid ultrasonic cleaners, chemical agents, and high temperatures, which can lead to dehydration (loss of water) and destruction of the mineral's structure. It is brittle and soft, so it should be protected from impacts and scratches. ## Storage It is recommended to store specimens in stable conditions, in closed “micromount” boxes that protect against dust, moisture, and mechanical damage.

Sources

IMA Mineral List (CNMNC)